Allow renaming Github file dependencies

Description

I attempted to include two Github file dependencies with the same filename: Helpers.fs. It's a terrible name, to be certain, but it is common, and I don't know of a way within paket.references to disambiguate. If some means already exists, I apologize for overlooking it. I tried a few options, and nothing appeared to work.

Repro steps

1. Add the following dependencies to a paket.dependencies file:
   github isaacabraham/fsharp-demonstrator src/FootballLibrary/Helpers.fs
   github isaacabraham/fsharp-demonstrator src/SuaveHost/Helpers.fs
2. Add the following lines to the project's paket.references file:
   File:Helpers.fs .
3. As an attempt at disambiguation, I tried the following:
   File:src/FootballLibrary/Helpers.fs ./Helpers.fs
   File:src/SuaveHost/Helpers.fs ./SuaveHelpers.fs

Expected behavior

I was uncertain what might happen. I would propose the following:
Allow disambiguation by specifying the full file path used in the paket.dependencies file.
I think the use of ./SuaveHelpers.fs for the second file would have worked as expected, but if not, I would like if we could change the target file name using the above approach.

Actual behavior

Only src/FootballLibrary/Helpers.fs is added to the project.

Known workarounds

I manually linked to the file in paket-files from my .fsproj and made sure not to specify that the link was maintained by <Paket />. This seems to work, as the first Helpers.fs is always retrieved due to either dependency order in paket.dependencies or alphabetical ordering of the folders within paket-files.

Related information

• Operating system: Windows Server 2012 R2
• Branch
• .NET Runtime, CoreCLR or Mono Version: .NET 4.6
• Performance information, links to performance testing scripts

Start by tracing how the paket.dependencies GitHub file entries are resolved into paket-files and how paket.references maps them into the project. Review the conflicting Helpers.fs reproduction, including the attempted path and target-name forms, then inspect the generated .fsproj links. Done means both dependencies can be referenced unambiguously with the proposed path or rename syntax.